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Abstract

Background

Gastro-Esophageal Reflux Disease (GERD) defined as a condition that develops when
the reflux of stomach contents causes troublesome symptoms and/or complications. Many
drugs are used for the treatment of GERD such as omeprazole (a proton pump inhibitor)
which is a widely used antiulcer drug demonstrated to protect against esophageal mucosal
injury. Melatonin has been found to protect the gastrointestinal mucosa from oxidative
damage caused by reactive oxygen species in different experimental ulcer models. The
aim of this study is to evaluate the role of exogenous melatonin in the treatment
of reflux disease in humans either alone or in combination with omeprazole therapy.

Methods

36 persons were divided into 4 groups (control subjects, patients with reflux disease
treated with melatonin alone, omeprazole alone and a combination of melatonin and
omeprazole for 4 and 8 weeks) Each group consisted of 9 persons. Persons were subjected
to thorough history taking, clinical examination, and investigations including laboratory,
endoscopic, record of esophageal motility, pH-metry, basal acid output and serum gastrin.

Results

Melatonin has a role in the improvement of Gastro-esophageal reflux disease when used
alone or in combination with omeprazole. Meanwhile, omeprazole alone is better used
in the treatment of GERD than melatonin alone.

Conclusion

The present study showed that oral melatonin is a promising therapeutic agent for
the treatment of GERD. It is an effective line of treatment in relieving epigastric
pain and heartburn. However, further studies are required to confirm the efficacy
and long-term safety of melatonin before being recommended for routine clinical use.

Trial Registration

QA13NCT00915616

Background

Gastro esophageal reflux Disease (GERD) is defined as a condition that develops when
the reflux of stomach contents causes troublesome symptoms and/or complications [1]. Symptoms of GERD occur in approximately 14 to 20% of the population on at least
a weekly basis. Symptoms of GERD may result in a large burden on employers through
increased absenteeism and decreased performance while remaining at work impaired by
health problems [2].

Even though over 50 years have passed since the discovery of melatonin, the knowledge
on its physiological function is still not complete. The results of the researches
have provided the evidence that melatonin is synthesized not only in the pineal gland,
but also in different organs. A special attention has been directed to the digestive
tract where total quantity of melatonin is considerably greater than in the pineal
gland [3]. It was calculated that the gastrointestinal tract contains at least 400 times melatonin
than the pineal gland [4]. Although pineal melatonin acts prevalently in an endocrine capacity, extra-pineal
melatonin may act as an autocrine or a paracrine hormone [5]. It protects gastric mucosa against destructive activity of free radicals in stress-induced
ulcers and due to non-steroidal anti-inflammatory drugs and other gastrotoxic agents
[6]. Furthermore, Kato et al. [7] demonstrated the inhibitory action of melatonin on secretion of HCL and pepsin. Only
a few studies on gastrointestinal role of melatonin have been carried out on humans.

In view of melatonin's known gut regulatory functions, antidepressant and anxiolytic
properties, and its potentially beneficial effects on brain gut axis, it was hypothesized
that melatonin might serve as an effective agent for treating GERD.

Methods

Sixty subjects "60", suffering from GERD symptoms, were attending the outpatient clinics
of the Gastro-Enterology Center and Specialized Medical Hospital. Informed consent
was obtained from all patients to be included in the study, after explanations of
the nature of the disease and treatment options. All patients signed an informed consent
to be included in our study. This paper was approved by the local ethical committee of Mansoura University Hospital,
General Surgery Department.

All individuals were subjected to thorough history taking including: history of drug
intake, epigastric pain, upper gastrointestinal bleeding (hematemesis and/or melena),
dyspeptic manifestations and heartburn. They were also subjected to clinical examination
with special stress on: (a) General examination: pulse, blood pressure and temperature.
(b) Chest and heart examination. (c) Local abdominal examination for the state of
the liver, spleen and the presence or absence of ascites. They also underwent laboratory investigations: Complete blood picture, Urine and stool analysis and Liver function tests including
serum albumin, bilirubin, alanine transaminase enzyme (ALT), aspartate transaminase
enzyme (AST). The patients excluded from our study were; patients with cardiac disease,
patients with renal affection, and patients with liver diseases (drug induced, autoimmune
disease and viral hepatitis). In addition, patients on the drugs known to affect the
GIT motility (phenothiazines, anticholinergics, nitrates or calcium channel blockers)
excluded during the time of conduction of the study or the preceding two weeks. After
exclusion, 45 subjects were selected for evaluation by: a) Endoscopic Investigation:
subjects were subjected to upper gastrointestinal endoscopy for visualization of the
mucosa of esophagus and stomach for the presence of mucosal ulceration. b) Record
of esophageal motility by Smart graph analysis software lab motility system Sandhill
8 - channels esophageal manometry. Manometric recording systems rely on computers
for data acquisition display and analysis. This manometric recording was done by using
station pull through technique at 5 minutes intervals. The most important aspect of
Lower Esophageal Sphincter (LES) pressure measurement is that of LES relaxation. Subjects
with duodenal, gastric ulcers or functional dyspepsia were excluded and finally 27
subjects with GERD were selected to complete the study compared with nine healthy
volunteers who matched with age and sex as controls or reference.

After admission the following was done: (a) blood samples for measuring serum melatonin
levels taken at 10.00 p.m., 2.00 a.m. and 6.00 a.m. After collecting the sample, the
blood centrifuged and serum thus was obtained and frozen at the temperature of minus
80°C. Melatonin concentration was measured with ELISA method using the Lab system
Multiscan and antibodies of the Immuno-Biological Laboratories (catalogue RE 54021)
[8]. (b)An ambulatory digitrapper was used to perform 24 hours pH-metry measurement by
UP S2020 Orion MMS Holland pH-metry. The pH probe was positioned 5 cm above the position
of the LES. The data were collected using De-meester (DM) score; gastroesophageal
reflux considered as a drop in esophageal PH below "4" and the percentage reflux in
24 hours calculated for each patient [9].

Basal Acid Output (BAO)

At the end of each pH-metry monitoring period, the electrode was removed and BAO was
measured during one hour through a naso-gastric tube inserted at the most dependent
part of the stomach. The correct position of the tube was checked by the water recovery
test. Patients were laid in a semi-recumbent position on their left side. Gastric
secretion was aspirated continuously by gentle manual suction and collected in 15-minute
samples after discarding the first 15-minute collection corresponding to the emptying
of the stomach. The concentration of H+ ions was determined on each sample by a titrimetric method with NaOH 0.1N and expressed
in millimoles H+ per litre. BAO is the sum of the four 15-minute outputs and is expressed in mmol H+/h.

Determination of serum gastrin levels

The serum gastrin concentration was measured by a radioimmunoassay method using C-terminal-directed
antibodies equally reactive to little gastrins (G-17) and big gastrins G-34. Serum
Gastrin was expressed in picograms per milliliter.

Groups: The subjects selected were classified into four groups: Group I included nine
healthy normal subjects and was considered the control group. Group II included nine
patients suffering from GERD; receiving melatonin alone for treatment of GERD in a
dose of 3 mg once daily at the bedtime [10]. Group III included nine patients suffering from GERD, receiving omeprazole alone
for treatment of GERD in a dose of 20 mg twice daily [11]. Group IV included nine patients suffering from GERD receiving omeprazole and melatonin
for treatment of GERD in the same dose of each of them. The three patient groups were
re-evaluated after 4 weeks and 8 weeks of treatment.

Statistical Analysis

The statistical analysis was performed using the SPSS statistical Package version
13.0 (SPSS, Chicago, IL, USA). To compare the data, the recorded values were expressed
as means and standard deviation (Mean ± SD). The minimal level of significance was
identified at p < 0.05 [12].

Table 1. Comparison of control subjects and patients pretreated with melatonin, omeprazole
and both (n = 9)

Table 2 illustrates that treatment with melatonin for 4 and 8 weeks leads to marked improvement
of GERD symptoms regarding heartburn and epigastric pain. There was also a significant
increase in the tone of the LES in the form of increased LES pressure, a significant
increase in the residual pressure, a significant decrease in the relaxation duration,
a significant increase in the relaxation percentage, a significant increase in the
pH with a significant decrease in BAO, and a significant increase in serum gastrin
and mean melatonin levels relative to pretreated patients.

Table 3 illustrates that treatment with omeprazole for 4 and 8 weeks leads to marked improvement
of GERD symptoms regarding heartburn and epigastric pain. There was also a non-significant
change in the tone of the LES, a non-significant change in the residual pressure,
relaxation duration, relaxation percentage, a significant increase in the pH with
a significant decrease in BAO, a significant increase in serum gastrin and a non -
significant increase in the melatonin level.

Table 4 illustrates that treatment with melatonin and omeprazole for 4 and 8 weeks leads
to marked improvement of GERD symptoms regarding heartburn and epigastric pain. A
significant increase in the tone of the LES in the form of increased LES pressure
also noted. In addition, there is a significant increase in the residual pressure,
a significant decrease in the relaxation duration, a significant increase in the relaxation
percentage, a significant increase in the pH with a significant decreased in BAO and
a significant increase in serum gastrin and melatonin levels.

Table 4. Effects of melatonin and omeprazole on patients with GERD group IV (n = 9)

Table 5 illustrates that treatment with melatonin alone or combined with omeprazole (Group
II & IV) leads to a significant increase in the tone of the LES in the form of increased
LES pressure. Also, there is a significant increase in the residual pressure, a significant
decrease in the relaxation duration, a significant increase in the relaxation percentage
compared with patients treated with omeprazole alone (group III), while patients treated
with omeprazole alone or combined with melatonin (group III & IV) showed a significant
increase in PH and serum gastrin level with a significant decrease in BAO than melatonin
alone (group II)

Discussion

Melatonin, a close derivative of serotonin (5-hydroxytryptamine, 5-HT) [13], is a hormone initiating sleep in humans [14] and a powerful scavenger of free radicals. It is more effective than several well-known
vitamins [15]. The pineal gland is the major source of melatonin in the peripheral circulation,
producing melatonin in a distinct circadian fashion, with peak levels occurring during
the night [13]. Melatonin has been also detected in entero-endocrine (EE) cells of gastro-intestinal
tract (GIT) wall, where this indole may act via endocrine, paracrine and/or luminal
pathway through G-protein coupled receptors [16]. Following pinealectomy, the light/dark cycle of plasma melatonin levels disappears,
while its daytime blood concentrations are attenuated but sustained mainly due to
its release from the GIT, and therefore, a part of blood melatonin has a source in
the digestive system, especially during daytime [17].

In the present study, the mean melatonin level was significantly lower in all patients
in comparison to control group at baseline evaluation. This observation is in agreement
with Klupiñska et al [18] who found that in patients with GERD and recurrent duodenal ulcers, melatonin concentration
was lower than in healthy subjects and concluded that high or relatively correct secretion
of melatonin is sufficient to prevent peptic changes in esophageal and duodenal mucosa.
In addition, Bubenik et al. [19] demonstrated that pigs with chronic gastric ulcers exhibited lower contents of melatonin
in the gastric mucosa and in the blood suggesting that these spontaneous ulcers originate
from the local deficiency of the indole.

However, Otsuka et al. [20] reported that acute stress induced gastric lesions in rats are accompanied by increased
plasma melatonin. The proposed explanation for the rise in melatonin is that its production
increases under stressful stimuli in both, experimental animals and human as suggested
by Karasek and Winczyk [21].

For the clinical purposes, some investigators measure serum concentration of melatonin
twice, that is at 9.00 a.m. (light period) and 2.00 a.m. (dark period) and the differences
in the day/night patterns taken for evaluation [22]. The interests of gstroenterologists mainly focused on studies on melatonin nocturnal
secretion. In other investigations, melatonin concentration in blood measured at three
points of time: at 10.00 p.m., 2.00 a.m. and 6.00 a.m. as done in our study as during
these hours the influence of food intake on enterohormones secretion is negligible.
On the other hand, at bedtime the patients often complain of recurrent symptoms of
GERD that largely disturb their sleep [17]. It was also noted that pharmacologically administered low and high doses of melatonin
have been found to be with very low or no toxicity [23].

The current study also evaluates the role of the recently used antiulcer drug melatonin,
the widely used antiulcer drug omeprazole and the combination of both drugs in the
treatment of GERD. We used an oral fast release melatonin at a dose of 3 mg/day for
4 and 8 weeks. Werbach [24] found that melatonin up to 6 mg at bedtime may be an effective treatment for GERD
with fewer and less serious adverse effects. It was found that treatment of GERD with
melatonin, omeprazole or both was duration dependent. Patients treated with melatonin
for four weeks and patients treated with omeprazole for four weeks showed incomplete
improvement of GERD symptoms. These findings are in agreement with Gavert and Harvey
[25]. Moreover, in patients treated with melatonin for eight weeks and patients treated
with melatonin and omeprazole for four weeks, there was complete improvement of GERD
symptoms as heartburn and epigastric pain. These findings were in agreement with Pereira
[26] who reported that dietary supplementation containing melatonin and L-tryptophan,
which is a substrate for melatonin biosynthesis in patients with GERD, resulted in
remarkable remission of GERD symptoms in the majority of treated patients. The clinical
remission of GERD was comparable with that obtained by classical treatment using omeprazole.
It was concluded that the formulation containing melatonin or its precursor, tryptophan,
promotes regression of GERD symptoms without any side effects and may be useful in
the GERD therapy. Melatonin has also been studied in alleviating GERD. In a head-to-head
comparison, the researchers gave 175 patients standard treatment with the prescription
drug omeprazole, while 176 received a supplement containing melatonin, its precursor
L-tryptophan, and B vitamins, over a 40-day treatment period. All patients in the
supplement group reported complete regression of symptoms by the end of the study,
compared with only 66% in the drug-treated group. Again, no significant side effects
were reported in the supplemented patients [26].

Although many studies were carried out to evaluate the role of melatonin in GERD based
on its effect in alleviation of GERD symptoms only, the review of literature showed
that no previous studies were based on endoscopic findings besides the clinical improvement.

It was believed that melatonin protects against GERD by increasing blood flow and
anti-inflammatory molecules in the esophageal mucous, thus preventing significant
esophageal injury [27]. Although, Sener-Muratoglu et al. [28] previously compared the antiulcer and gastro duodenal protective mechanism of famotidine,
omeprazole and melatonin and their results revealed that the three drugs have gastroduodenal
protective action but famotidine and omeprazole have lowering effects on gastric acidity
(antisecrotory activity) whereas melatonin has no effect on this parameter but famotidine
and omeprazole were not efficient as antioxidant as melatonin.

However, others concluded that the esophagoprotective activity of melatonin against
GERD might be related to the inhibitory effect of this indole on gastric acid secretion
and due to stimulation of gastrin release, which might attenuate the gastro-esophageal
reflux by stimulation of the contractile activity of the lower esophageal sphincter
[29].

In the present study, there was a significant increase in the pH with a significant
decrease in BAO and a significant increase in serum gastrin after melatonin therapy
compared to pretreatment levels. While patients treated with omeprazole alone or combined
with melatonin showed a significant increase in PH and serum gastrin level with a
significant decrease in BAO than melatonin alone, however, the combined therapy showed
a non-significant increase in serum gastrin or BAO compared with omeprazole alone.

These protective effects were accompanied by gradual increase in plasma melatonin
levels suggesting that topical melatonin exerts a local protective action on gastric
mucosa, acting via circulation following its absorption form the gut. The results
of our study revealed that melatonin has a role in the improvement of GERD as detected
in patients treated with melatonin for 8 weeks and in patients treated with melatonin
and omeprazole for 4 weeks. Meanwhile, omeprazole alone has a better effect on gastric
acidity than melatonin alone as the clinical improvement started at the fourth week
of treatment with omeprazole and was completed at the eighth week. On the other hand,
with melatonin alone the improvement started at the fourth week and was completed
at the eighth week of treatment but it was significantly less effective than omeprazole.
It was found that melatonin accelerates the clinical and endoscopic improvement when
combined with omeprazole as improvement in combination therapy was completed at shorter
duration (at the fourth week) with no further increase in serum gastrin level. Our
results were in agreement with Bandyopadhyay et al. [30] who stated that melatonin prevented gastric damage and when compared with already
marketed anti-ulcer drugs such as ranitidine and omeprazole, melatonin was found to
be more effective than ranitidine but less effective than omeprazole in preventing
stress ulcer. They also demonstrated that co-treatment of GERD with melatonin at a
low dose synergistically increases the efficacy of omeprazole in preventing stress
induced lesion. This may be important, as giving omeprazole at lower doses would reduce
the severity of their side effects. Rieter et al. [31] reported that melatonin when combined with other anti ulcer drugs like omeprazole
has a beneficial effect as it accelerates the healing effects of omeprazole and shortens
the duration of treatment. Therefore, melatonin reduces the side effects and increases
the efficacy of omeprazole.

Conclusion

From the results of our study, it can be concluded that melatonin could be used in
the treatment of GERD either alone or in combination with omeprazole. The combination
therapy of both melatonin and omeprazole is preferable as melatonin accelerates the
healing effect of omeprazole and therefore shortens the duration of treatment and
minimizes its side effects.

Abbreviations

Competing interests

Authors' contributions

The manuscript has been seen and approved by all authors. TSK & AAM write the paper. TSK & AE designed research. TSK, AAM, AE & AMA performed research. TSK & AMA analyzed data.

Acknowledgements

The authors thanks all sample donors for their contribution to this work. The authors
are grateful to Prof Dr Nabiel Gad El-hak "prof. of surgery" and all members in the
motility unit, gastroenterology center, Mansoura, Egypt.

This paper has been linguistically revised by Dr Ahmad Hassan Ali, Lecturer of English
Linguistics, Port Said Education Faculty, Department of English and proof reader of
Suez Canal University, Port Said Branch, Graduate of USC, L.A., California, USA. ESP
instructor, course designer and proof reader, Chief translator of Mansoura University
ESPRC from 1990 till 2006.